1. Field of the Invention
The invention relates to a method for shaping glass on a microscopic scale utilizing self-inflation.
2. Description of the Prior Art
Glass blowing is an art that dates back over 2000 years. Today, glass blowing is used in a wide array of applications, including scientific glassware, optical components, consumer glass containers, and visual arts. Although blow-molding techniques are used in the glass industry to automate the fabrication of bottles and other containers, many fine glass products are still shaped one at a time by glass blowers.
The property that enables the successful shaping of glass is that its viscosity is highly dependent on the temperature. In order to shape glass it needs to be heated above its softening point, i.e., the temperature at which glass has a viscosity of 106.6 Pascal-seconds (Pa-s) (about 800° C. for borosilicate glass). In conventional glass blowing, a gob of glass is first heated inside a furnace. The gob is then removed from the furnace and blown into desired shapes. Often the heating and blowing steps are repeated multiple times. Once the glass is shaped, it is usually annealed to remove stresses that developed during the blowing. The original implementation of micro-glass blowing was a direct adaptation of conventional glass blowing techniques on a microscale, i.e., to bond a glass wafer to a through-etched silicon wafer, heat the bonded wafers, and directly apply fluidic pressure through the etched holes in order to blow spheres—described in US Patent Application Publication 2007/0071922.
Microspheres have been fabricated in the past using different fabrication methods. For example, see: R. Cook, “Creating Microsphere Targets for Inertial Confinement Fusion Experiments”, Energy & Technology Review, pp. 1-9, April 1995; R. Dagani, “Microspheres Play Role in Medical, Sensor, Energy, Space Technologies”, Chemical and Engineering News, pp. 33-35, December 1994. However, previously fabricated microspheres are not attached to a substrate and can only be filled with certain light gases (e.g. hydrogen) through diffusion.